Google's core business is search and advertising. So why is it doing buying a bunch of drones and robots? It sounds like something out of a sci fi novel.

But in fact, they're both long-term, strategic bets.

The third phase of the Internet.

Google is basically in its third phase. It's already mastered search and advertising, which were core desktop activities in the mid-2000s. Mobile came next, with its Android platform.

Both of those have given Google a massive audience. In February, Google saw 187 million unique visitors on desktop alone, making it the most-visited web property in the U.S., according to ComScore. The entire web received 222 million uniques that month — so you can see that Google is literally running out of Internet.

In order to keep growing, Google needs more people. Not just a few million more. Only hundreds of millions of new users will keep Google growing meaningfully. This is a practical problem for the company: There is no point in Google acquiring a company that has 50 million users, for instance. It just wouldn't move the needle.

There is only one place that hundreds of millions of untapped users exist: offline.

In order to reach these people, Google needs the entire world to have Internet access. (Facebook has also recently woke up to this third phase, with CEO Mark Zuckerberg's Internet.org project which has much the same goals.)

Google has already announced Project Loon to bring Internet access to parts of the world without it, and offers Google Fiber for high-speed access. With drones, the company could bring Internet access to millions of people, and even help with disaster relief.

Why robots are the future.

With robots, Google is betting on the future in a different way. Given Google's obsession with knowledge and organizing information, we could see Google beefing up its search offerings with artificial intelligence from Boston Dynamics, which is a leading provider of human simulation software. Its robots need to react independently to their environment — and perfecting that type of machine-learning is widely regarded as the key to the next phase of tech.

With Google's Titan acquisition, it likely sees it as a way to advance Project Loon, as well as advance its imagery with Google Maps and Google Earth.

Project Loon began with a pilot test in June 2013, but there's still no word on the official launch date.

So while the drones and robots may seem speculative and whimsical — like something from a movie — they're really strategic bets that will take years or decades to pay off. Yet they're also both crucial if Google is to continue growing.

The drones will find new users and get them online. The robots will make it easier for new users to understand the web once they get there.